**2.2. Hierarchical paradigm**

Distributed processing encompasses a wide range of task autonomy and semantic richness in hierarchical architectures. This paradigm describes implementation labels that employ vertical delegation for management functionality. Hierarchical approach includes distributed objects and limited forms of Management-by-Delegation (MbD) with code mobility technologies such as Remote EValuation (REV) and Code-on-Demand (CoD). Distributed objects describe a form of gateway operation allowing the communication with encapsulated data and actions remotely. Likewise, REV provides code for execution of intended management function while CoD retrieves and caches code to execute the intended management function [6]. The hierarchical paradigm supports the delegation as following:


from the details of the management task. Likewise, this method of delegation statically retrieved low-level data from simple agents before handing the response data to the central authority for processing into information.

a network through a TCP/IP handshake paradigm. The client requests information, while the server responds when its advertised services are accessed. This each request/response, as depicted in **Figure 1**, is a complete round trip on the network. The code that implements these services i.e. the know-how is hosted locally by the server, also server has processing capabilities. Client decides with some intelligence which of services offered by server it should use.

Evolution and Paradigm Shift in Distributed System Architecture

http://dx.doi.org/10.5772/intechopen.80644

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Single-tier architecture is the simplest, single tier on single user, and is the equivalent of running an application on a personal computer as shown in **Figure 2**. All the components like user interface, business logic, and data storage, which are necessary to run an application, are located within the system. They are the easiest to design, but the least scalable as they are not

Two-tier architectures supply a basic network between a client and a server. For example, the basic web model is a two-tier architecture as illustrated in **Figure 3**. A web browser makes a request from a web server, which then processes the request and returns the desired response, in this case, web pages. This approach improves scalability and divides the user interface

part of a network also they cannot be used for designing web applications [9].

**3.1. One-tier architecture**

**3.2. Two-tier architecture**

**Figure 1.** Client server paradigm.

**Figure 2.** Single-tier architecture.

